Capture HDMI to Portable Hard Drive

[Keith Knuth]

It would seem that HV20 users would be salivating for a portable hard drive that connected to the camera via HDMI. This way you could capture full HD resolution footage from the camera on the go and without a tape.
Do you think anyone will figure out how to do this?
Would it be prohibitively expensive to make?

[Colin Gould]

Note that it would be uncompressed, not just full resolution (1920x1080), which would mean a LOT of space.
It's not clear yet if the HDMI output is actually pre-HDV compression or other processing (even the 1440 vs 1920 res scaling), so you might not actually gain anything vs firewire, see other threads...

also are other threads earlier about capturing via firewire to drives (works but not perfect as doesn't start/stop w/ button.)

[Wes Vasher]

It would be very, very expensive today, think mini-Wafian. The video would have to be compressed somehow though as you'd have to have a crazy multi-drive raid or expensive flash memory array to save uncompressed as far as I know.

The cheap way to go is build/buy a PC and portable-ize it yourself. Probably could build something like that for $1000-$2000.

[David Garvin]

Originally Posted by Colin Gould

also are other threads earlier about capturing via firewire to drives (works but not perfect as doesn't start/stop w/ button.)

I searched this forum but didn't find any info about people doing this with the HV20. My guess is that it would work, but maybe somebody could run their HV20 through the paces on this front and let us know.

[Mathieu Kassovitz]

http://www.dvinfo.net/conf/showthrea...338#post658338

[George Anthonisen]

Originally Posted by Colin Gould

also are other threads earlier about capturing via firewire to drives (works but not perfect as doesn't start/stop w/ button.)

Sony has a HDD out specifically built for this task that connects via firewire and DOES start/stop with the cam. It records in parallel the tape, and you can even edit right on it. It's NOT cheap though!

http://www.amazon.com/HVR-DR60-Recor.../dp/B000IF9OVS

[Harm Millaard]

I have posted about this earlier, but HDMI is nothing more than a fire wire or other digital interface once you have the material on tape. Once on tape the original signal has been heavily compressed and no matter what you do, you can not get back the uncompressed material. IMO HDMI is getting to be a hype for people who do not understand what it is for, same as with 24P, which is also a hype 'to get the filmic look'.

[Pat Reddy]

I have the HV20 connected to a projector right now (only 720p) but the PLAY/OUT SETUP2 menu screen says "HDMI OUT 1920x1080i". This suggests that the camera thinks it's uncompressed or "pre-HDV". Maybe it goes from HDV back to 1920 by 1080i for playback, but what about live capture?

Pat

[Harm Millaard]

Originally Posted by Pat Reddy

I have the HV20 connected to a projector right now (only 720p) but the PLAY/OUT SETUP2 menu screen says "HDMI OUT 1920x1080i". This suggests that the camera thinks it's uncompressed or "pre-HDV". Maybe it goes from HDV back to 1920 by 1080i for playback, but what about live capture?

Pat

Hope this explains it somewhat.

[Ian G. Thompson]

Harm, I always understood what you just mentioned to be true... the recording on tape is always HDV standard (1440x1080 4:2:0 colorspace) and when feeding that 'recording" through the HDMI output it is blown up to 1980 x 1080..etc.

But ....for "live" feed through the HDMI output to a hard drive the question still remains...is it true 4:2:2 with little to no processing (avoiding the HDV compression)?? I have read several different people's theories on this but nothing conclusive.

I have also read that even with the uprezzed footage from tape through he HDMI the colorspace is somehow at 4:2:2. Some have questioned that and made statements like "how can you get information that was never there to begin with"..etc.

It is sort of confusing for a lot of us when he says this and she says that etc. and to top it off we get no specific information from the manufacturer about this. What I "think" i always understood was HDMI supports 1980x1080 and 4:2:2 colorspace. So I have to believe that is exactly what is being fed through that type of output.

edit: Ok you posted while I was typing. So my question to you is...is it still compressed during a live feed? I have read where others have done their own test and said the colorspace is 4:2:2. How can they get that out of 4:2:0?

[Ian G. Thompson]

By the way...hello ya'll...been lurkin here for a while...sorry for the late introduction.

[Harm Millaard]

Originally Posted by Ian G. Thompson

Harm, I always understood what you just mentioned to be true... the recording on tape is always HDV standard (1440x1080 4:2:0 colorspace) and when feeding that 'recording" through the HDMI output it is blown up to 1980 x 1080..etc.

But ....for "live" feed through the HDMI output to a hard drive the question still remains...is it true 4:2:2 with little to no processing (avoiding the HDV compression)?? I have read several different people's theories on this but nothing conclusive.

I have also read that even with the uprezzed footage from tape through he HDMI the colorspace is somehow at 4:2:2. Some have questioned that and made statements like "how can you get information that was never there to begin with"..etc.

It is sort of confusing for a lot of us when he says this and she says that etc. and to top it off we get no specific information from the manufacturer about this. What I "think" i always understood was HDMI supports 1980x1080 and 4:2:2 colorspace. So I have to believe that is exactly what is being fed through that type of output.

edit: Ok you posted while I was typing. So my question to you is...is it still compressed during a live feed? I have read where others have done their own test and said the colorspace is 4:2:2. How can they get that out of 4:2:0?

Ian,

When I made this chart or whatever you want to call it, I wanted to confirm that I was not mistaken or misrepresenting things, so I contacted David Newman, who IMO is one of the most knowledgeable guys around here, and in essence he confirmed this was in general an accurate description of HDMI. He noticed that the data rate I mentioned was too high and should be around 120 MB/s, since the signal from HDMI is only 4:2:2 and not 4:4:4.

Furthermore, David told me that the Sony cameras with HDMI first compress the signal to 1440x1080, then prior to outputting convert it back to 1920x1080 and then put it on the HDMI channel. I do not know about the Canon cameras and how their HDMI works.

I hope I have been relatively clear.

[Ian G. Thompson]

Oh yes you were abundantly clear and the chart was very decriptive thanks. I jumped in this thread because I agreed with keith's statement about users salivating for a portable hard drive to use with HDMI...and I agreed with your peception about peoples lack of understanding (understandably) when it comes to HDMI (me included). My original staement was to feed off both your statements to see if we could get any more information on this camera in particular.
Yeah, I read about how Sony implements their footage through HDMI. And I also thought 200 MBps was kind of high.. 120 with 4:2:2 is what I remember.

[Harm Millaard]

Ian,

As you I have often wondered how it could be possible that HDMI does NOT carry a price tag of $ 3.000, which happens to be the main difference between the Canon A1 and G1, and where the difference is the HD-SDI interface and still deliver the same functionality? I just don't get it. It seems like a major USP to me. Still the capabilities of HDMI are the same as HD-SDI in theory. I would be interested to hear practical experiences from users.

It would be worthwhile to have some of the experts here chime in and give their expert opinions, since a lot of people here are anxious to get this cleared up. Does HDMI give out a 4:2:2 signal and how does the up-converting work when starting with a 4:2:0 tape recorded signal?

[Peter J Alessandria]

Originally Posted by Harm Millaard

It would be worthwhile to have some of the experts here chime in and give their expert opinions, since a lot of people here are anxious to get this cleared up. Does HDMI give out a 4:2:2 signal and how does the up-converting work when starting with a 4:2:0 tape recorded signal?

Much of this discussion is over my head but.... does this mean there might be a potential advantage to capturing video from my HV20 via an HDMI capture card (like Black Magic) as opposed to using firewire?